Air conditioning control



Sept? 1936- M. ANDERSON ET AL Re. 20,083

AIR CONDITIONING CONTROL Original Filed May 9, 1931 3 Sheets-Sheet l IN VEN TORS.

i M. ANDERSON, By Passer TI PAL/wee,

A TTORNEYS.

iept- 19354 5. M. ANDERSON El AL Rg. 20,083

AIR CONDITIONING CONTROL Orizinal Filed May 9, 1931 3 Sheets-Sheet 2 HUM/DIFIEE 64 wnrsle .SUPPLY HUMIDIFIEE INVENTORS. 5. M. Arvoeeso/v, Posszr T PALME A TTORNEYS.

Sept. 1, 1936'. M: ANDERSON rim. 1 20,033

AIR CONDITIONING CONTROL 3 Sheds-Sheet 3 Original Filed May 9, 1931 E i i 3 m n W Y 0 WZ'T BULB TEMPER/ZTURE IN VEN TORS. 5. M. ANDERSON,

. By E0522? 7". PALMER,

M 64m QMLIMM A TTORNEYS.

UNITED STATES PATENT OFFICE.

AIR CONDITIONING CONTROL Samuel M. Anderson and Robert T. Palmer,

Sharon, Masa, asslgnors to B. F. Sturtevant Company, Boston, Mass.

Original No. 1,881,992, dated October 11, 1932, Serial No. 536,144, May 9, 1931. Application for .reissue July 19, 1935, Serial No. 32,292

22 Claims. 236-44) I'his invention relates to methods and apa lower temperature than that existing within paratus for controlling the vapor content of the room.

fluids and relates more particularly to meth- Another object of theinvention is to prevent ods and apparatus for controlling the relative the condensation of moisture upon the window humidity of the air within an enclosure. pane of a room.

It is becoming better and better known that Another object of the invention is. to autoliving conditions in heated rooms are greatly matically control the supply of moisture to the air improved when the air within the 'rooms conwithin a room having a surface exposed to outtains a substantial amount of moisture or side temperatures, by observation of the wet bulb ll) water vapor which tends to prevent the dryand dry bulb temperatures within the room,'and

ing of the nasal and throat passages of the the temperature of the air outside the room. occupants. This moisture also tends to pre- Another object of the invention is to autovent the circulation of dust, which in itself matically control the supply of moisture to the air is undesirable and may be injurious. Also, in withina room by holding the dew point of the 10 certain manufacturing processes, among which room just under the inside temperature of a surare the manufacture of paper and the manufacface exposed on one side to the room temperature of cloth, the presence of a certain amount or ture and on the other side. to the outside air. moisture is necessary in the air in which the It is well known that when air contains moisprocesses are employed. The heating systems genture this moisture will be precipitated if the air erally employed for heating buildings effectively is cooled to a sufilciently low temperature known 20 reduce the relative amount of moisture in the air as the dew point. The moisture from the air so that it has been found desirable to provide 7 which condenses upon the inner surface of the humidifying apparatus for introducing additional window pan is Precipitated y the in on t moisture to compensate for the loss of relative with and adjacent to the window pane being humidity through the heating process. cooled by the relatively cold window pane to its 25 A relative humidity of from fifty (50%) to dew point. Obviously, the ater the amount of fifty-five (55%) percent is in many cases desirmoisture in the air of a room, the higher the temable, but in cold weather and especially in experature at which it will precipitate upon the tremely cold weather, such a high degree of .moiswindow pane, and the less the amount of moisture in the air of a closed room is attended by a, ture, the lower the temperature at which the 30 serious disadvantage, in that a low outdoor temmoisture will precipitate. Since a room, the air perature chills the window panes of the room, of which it is desired to humidity, ordinarily has causing the moisture in the air of the room to one or more windows exposed to the outside aircondense thereon, and if this condensation is exthe relative humidity of the air within the room cessive, the window pane becomes i'rosted or cannotbe held at a constant value when outside 35 clouded and the view is obscured. In many, cases temperatures change. It is desirable to have a it may be desirable that the moisture content con t ve d y nd 8- constant temof the air in a room be as high as possible without Deratn e w thin 8 room, but it is undesirable to producing thiscondensation of the moisture on have the window panes of the room become the window surface, but due to the wide range of clouded D y e de sation of the moisture outdoor temperatures during the winter months, m the conditioned 1- t has, therefore, been and the resulting difieren e in ta"went-lurev necessary to reduce the relative humidity of the tween the heated air in the room and the outside 1 within a room the Outside temperature air, the relative amount of moisture which can crops in order to prevent condensation on the be supplied to the room without causing con- 3 ;21 522; f zgz g ygg 23122 1 2 353; figl i tztion will correspondingly vary within wide t i g g the i hum g of the 12 as on s e c anges o mpera ure occur hold An obJect of the invention is to control the the relative humidity as high as is possible with Vapm' contentflf v out the condensation of the moisture upon the 50 Another obJect of the invention is to autowindow panes, mat a ly Control t pp of moisture to the In one embodiment of the invention, analyses air within a. room, by observation of the condiare m de of the eb b lb and dry b lb temperations which would cause the condensation of tures of the air within the room and 01 the outmoisture from the air on a surface exposedv to side temperatures and control apparatus is ac- 55 tuated to prevent the amount of moisture in airintheroomirombecomingsogreattbatthe dew point 01' the air at the window pane becomes the same as, or approachesclosely the inside temperature of the window pane. Experiments were made to determine for argiven of outside temperatures, the wet bulb and dry bulb temperatures within the room at which condensation would occur for each outside temperature, while holding the relative humidity as high as prac;

ticable. It was found that for each value of outside temperature, moisture would condense onthe window pane of the room at a certain wet bulb tional to the wet bulb temperatures of the air within the room, a dry bulb thermocouple arranged within the room to generate electro-motive forces proportional to the dry bulb temperature within the room, a pair oi. dry' bulb themacouples placed without the room exposed tothe outside air to generate electro-motive forces proportional to the temperature of the outside air and a difierentially wound galvanometer having its moving coil adapted to actuate control apparatus .to control the humidifier supplying the moisture to the room. One difierential coil of the galvanometer is connected to one of the thermocouples outside the room and the other differential coil 01' the galvanometer is connected to the thermocouple which is responsive to wet bulb temperatures within the room. The windings of the difierential coils are so arranged and the electro-motive Iorces generated by the thermocouples are adjusted so that when the -wet bulb.

- temperature, 01' the air within the room, in-

creases above a predetermined condensation level .at a given outside temperature, the magnetic fields set up around the two-differential coils are such that the moving coil maintains its pointer against the contact which actuates control circuits to shut off the humidifier The direction of rotation of the moving coil is arranged with respect to the magnetic field set up by the diflerential coils so that the control contacts are kept closed when higher wet bulb temperature or a lower outside temperature is reached, but to open the contacts when the wet bulb temperature is too low to cause the precipitation of moisture at a given outside temperature.

The dry bulb temperature control apparatus comprises two galvanometers, one having its moving coil connected to the other 01 the thermocouples outside theroom and the other having its moving coil connected to a dry bulb thermocouple inside the room. The moving coil 01 the galvanometer, associated with the thermocouple placed outside the room, carries a pointer which contacts with a resistance which is carried by the moving coil of the galvanometer associated with the dry bulb thermocouple inside the room. The pointer and the resistance are connected in a relay circuit and are so adjusted that when the dry bulb temperature drops for a given outside temperature 'below a predetermined condensation ,level, in-

the predetermined condensation level for a given outside temperature, the two galvanometer coils move relative each other to decrease the amount of resistance in the relay circuit, causing it to pull up its armature and turn on the valve in the humid- The, wet bulb temperature control and the dry bulb temperature control act jointly to control theeperation oi the humidifier. The humidifier is oil when eitherrthe wet bulb or the, dry bulb control act to shut oil the humidifier but is on only when both the controls act to turn In another embodiment of the invention a thermocouple responsive to wet bulb temperatures is placed adjacent a window pane or other surface exposed to outside temperatures, and a portion or the air within the room is passed in contact withthe window pane so as to be cooled thereby to a wet bulb temperature corresponding to the temperature oi. the window pane. A thermocouple responsive to dry bulb temperatures is mounted in the window pane, in contact with the window -pane, or exposed to the outside air to generate electro-motive forces proportional to the tempera- DOiht is reached and that the dew point is the point where the wet bulb temperatures oi. the 'air and,

the dry bulb temperatures'of the air are exactly responsive to the temperature of the window pane..

The two thermocouples are so connected to control apparatus that when the wet bulb temperatures and the dry bulb temperatures are substan-- tially the same, control apparatus is actuated to shut of! the humidifier until such time as the wet bulb temperature of the air immediately adjacent the window pane becomes less than the tempera-; ture of the window pane. This is done by causing the electromotive forces generated by the two thermocouples to oppose each other so that when they are substantially equal, contacts are closed in a control circuit to actuate control apparatus to shut oil the humidifier or to decrease the ture of the window pane. -It isknown that the. moisture in air precipitates only when its dew .equal. This is the condition when moisture conamount of moisture supplied to the air within the room.

The invention will now be explained with reierv couples co-operate to actuate a single control ap- Fig. 3 is a tic view of humidity control apparatus for decreasing the amount oi! moisture. supplied to the air within a room when the dry bulb temperature of a window pane of a room, and the wet bulb temperature of the air immediately adjacent the window pane become substantially equal;

Fig. 4 is a diagrammatic view showing another form of circuit for shutting oil? the humidifier when the temperature of the window pane of Fig.

3 and the wet bulb temperature of the air adjacent the window pane become substantially equal;

Fig. 5 is an end sectional view of a metal surface having radiative fins and air channels which may be used in the control apparatus shown by Figs. 3 and 4 for causing a wet bulb thermocouple to become responsive to temperatures proportional to the temperature of the outside air;

Fig. 6 is a side view showing the layout of the apparatus shown by Fig. 5 for receiving a wet bulb thermocouple, and

Fig. '7 is a chart having plotted thereon the wet bulb temperatures and the dry bulb temperatures for given values of outside temperatures at which the control circuits shown by Figs. 1 and 2 would become actuated, to decrease the amount of moisture supplied to the air within a room.

The co-ordinate of the curves on the. chart of Fig. 7 were chosen from a psychrometric chart and adjusted to meet actual working condition through knowledge gained from actual working tests. When the wet bulb and dry bulb temperatures are maintained on the curves of this chart for given values of outside temperature, the highest possible values of relative humidity are maintained within the room without condensation appearing upon the window pane. Of course, the relative humidities are low at low outside temperatures but this is a condition which cannot be avoided since with the present design of human habitations it is impossibleto have relatively high humidities within a room with windows exposed to very low outdoor temperatures without moisture condensing upon the window panes.

An inspection of the chart of Fig. 7 shows that at 50 outside temperature a wet bulb temperature of 62 and. a dry bulb temperature of 68 may be maintained without the condensation of moisture on the window pane. At zero degrees outside temperature, the desirable dry bulb temperature is 78 and the desirable wet bulb temperature is 52. An inspection of the slope of the curves shows that for an increase of 50 outside temperature, an increase of 10 wet bulb temperature and a decrease of 10 dry bulb temperature is permissible. while the outside temperature increases 50 and as the rate of increase is constant, it is seen that an increase of 2 of wet bulb temperature for each 10 of outside temperature is permissible. Likewise, a decrease of 10 dry bulb temperature is shown for an increase of 50 outside temperature, this rate of decrease of dry bulb temperature being -2 for each 10 of outside temperature. It is seen, therefore, that the rate of increase of wet bulb temperature to outside temperature is one to five and that the rate of decrease of dry bulb temperature to increase of outside temperature is one to five. Bearing in mind these relative changes of dry bulb and wet bulb temperatures, the operation of the apparatus shown by Figs. 1 and 2 will now be explained.

The dry bulb thermocouple I is placed outside the room in which the air is humidified and generates electro-motive forces proportional to outside temperatures. The electro-motive forces thus generated are fed into the moving coil II of the galvanometer 9 which has two moving coil armatures II and II. The thermocouple I2 is arranged within the room and is responsive to the dry bub temperature of the air within the room. The electro-motive forces generated by this thermocouple are responsive to the dry bulb temperature of the room and are fed through the resistance I3 into the other moving coil I4 of the galvanom- The wet bulb temperature increases 10 eter. The armature II carries the pointer 15 and the armature II carries the resistance I6, the pointer I5 and the resistance It contacting with each other and being so arranged that the amount of resistance in an electrical circuit including the pointer I5, the resistance IS, the battery I9; and the relay I1 is decreased when the moving coils I I and II move in opposite directions away from each other, and is increased when they move 7 towards each other. The armature 82, when the relay is'de-energized, is adapted to fall back and close a circuit, including the armature 82, the contact 83, the alternating current source 84, and the valve control motor I8, to cause the valve control motor to operate to close the valve 20 and to shut oil the supply of water from the water supply 2| to the humidifier 22. The two armatures of the galvanometer 9 are so arranged with respect to each other than when the dry bulb temperature affecting the thermocouple I2 is at a predetermined value or lower with respect to the temperature afiecting the thermocouple I0, responsive to the outdoor temperatures, the amount of the re sistance I6in the circuit of the relay I1 is too great for the relay to be sufficiently energized to pull up its armature 82 so that the humidifier remains shut off. When the temperature afiecting the dry bulb thermocouple I2 is above its prede termined value with respect to a given outside temperature afi'ecting the thermocouple Ill, the galvanometer coils II and I4 move away "rom each other, decreasing the amount of resistance in the relay circuit, energizing the relay, causing it to pull up its armature 82, to open the circuit of the valve control motor I8, and to open the valve 20 in the humidifier water supply The two moving coils II and I4 of the galvanometer 9 are wound inopposite directions so that while an increase in current in the moving coil I l causes it to move to the right in the direction indicated by its associated arrow, an increase in current through the moving coil I4 causes it to move to the left as indicated by its associated arrow. As a result, assuming a constant outdoor temperature which would cause the pointer I5 to remain stationary, an increase of the dry bulb temperature within the room would cause the thermocouple'IZ to generate increased currents. causing the moving coil I I to move to the left and so move the resistance IS with respect to the pointer I5, that less resistance is in the circuit of the relay I'I, so that increased current flows therethrough to energize same. Then, assuming a constant dry bulb temperature within the room, the moving coil I4 and its associated resistance I6 would remain stationary. Then, as the outside temperature affecting the thermocouple I0 increases, the moving coil II moves to the right carrying with it the pointer I5 which moves relative the resistance I6 to decrease the resistance in the relay I1 and increase the current flowing therethrough to energize the relay to cause the humidifier to be turned on. A decrease in the dry bulb temperature in the room, if the outside temperature remains constant, or a decrease in the outside temperature while the dry bulb temperature remains constant, causes the amount of resistance in the circuit of the relay I! to become greater. causing a decrease of current through the relay winding to deenergize it sufficiently to permit the armature 82 to fall back to close the circuit of the valve control motor I8 to cause it to shut off the humidifier.

Since the dry bulb temperature control appa ratus is designed to operate to shut off the humid-' ifier when the dry bulb temperature-is on or below the dry bulb temperature curve of Fig. 7, it will operate to actuate the control apparatus regardless-oi' any fluctuation oif the outside temperature or inside dry bulb temperature in either direction. To illustrate the operation, the following. conditions which would be met with actual installation will be described: r

' 1. The outside temperature increases while the to-cause. the armature 82 to be pulled up to open the humidifier valve. f

3. The outside temperature increases while the dry bulb inside temperature decreases, the temperatures remaining on the dry bulb temperature 1 curve of Fig. 7. -The increase. of outside temperature causes the moving coil it to moveto the right to tend to decrease the amount of resistance in the circuit, but the decrease of the dry bulb 'inside temperature causes the coil iii to move to the left to tend to increase the amount ofresistance i n the circuit, the combined movement of the two coils resulting in the amount of resistance in the circuit remaining constant, this 'amount of resistance, as has previously been explained, be-- 2 The moving coil I4 moves to the right to insert more resistance in the relay circuit, causing deenergization of the relay with its armature released, to shut oif the humidifier.

5. The outside temperature decreases while the dry bulb inside temperature increases to hold the moving coil ll moves to tend to place less resistance in the relay circuit, the degrees ofmovement of the two coils being the same, resulting in the resistance in the relay circuit being held the same and at the value previously described as being lnsuiiicient to energize the relay, causing the humidifier to be turned 01!. When the outside temperature decreases or the dry bulb inside temperature increases at rates suflicient to throw the temperatures above or below the curve oi Fig. 'l, the conditions will be similar to those of other of the items listed herein. 6. The outside temperature decreases while the dry'bulb temperature decreases. Both of the coils l4 and -II move to place more'resistance in the relay than is necessary to de-energize it, causing the humidifier to be shut off.

.7. The outside temperature remains constant while the dry bulb inside temperature increases.

The 'movingcoil I4 moves to the left to place less resistance'in the relay circuit,causing it to be energized to pull units-armature and to open the humidifier valve.

8. The outside temperature remains constant while the dry bulb inside temperature decreases. The moving coil l4 moves to the right to place more resistance in the relay circuit, causing the humidifier to be shut oflL. dry bulb temperature inside the room remains constant. The moving coil 1 l-moves to the right The resistance l3 in the menu; of the thermocouple I2 is adjustable to compensate for inequalities of response of the .two thermocouples or for other inequalities.

The dry bulk; temperature control apparatus described above actuates only to prevent the con-' densation'oi! moisture on the window pane. It; acts to shut oi the humidifier when conditions indicate that moisture may appear on the window pane and turns on the humidifier again when the tem eratures have so changed that there is .no dan r 01' moisture appearing. There is no attempt to have the control apparatus actuated for Y comfort purposes other than to turn on-the hutemperature and which forces are fed into the difierential field coil 24 oi. the galvanometer 25. The wet bulb thermocouple 26 is arranged within the wick 21 which is arranged in such position within the room that the air stream strikes against it to cause it to respond in the well known manner'to wet bulb temperatures and to generate electrq-motive forces proportional thereto.

These electro-motive forces generated by the thermocouple 26 are led through the resistance 29 and into the difierential coil 30 of the galvanometer 25. As shown by the wet bulb temperature.curve of Fig. 'I, the wetbulb temperatures increase from 52 to 62 while the outside temperatures increase from zero degrees to 50. There is a 10 increase in wet bulb temperatures to a 50 increase in outside temperatures. The

differential coil III is arranged to have five times as many ampere turns as the difierential coil 24 and these coils are wound in opposite directions so that the magnetic force from, the coil 24 infiuences the moving coil-3| of the galvanometer and opposes the magnetic force set up in the coil 30. The resistance 2! is adjusted until the ierce set up in the coil 30 by the thermocouple'at 52 wet bulb'temperature, for example, is equal to the force setup in the diilferential coil 24 corresponding to an outside temperature of 0 degree's. The magnetic forces set up by the coils 24 and 30 are seen to be equal and opposite as long as the wet bulb temperature within the room for a given outside temperature lies on the wet bulb temperature curve of Fig. 7. The moving coil 3| carries the pointer 32 which is just free from the contact 33, when the forces exerted by the coils 24 and 30 are equal, to, open the electrical circuit through the current source 34 and the relay 90, thus de-energizing the relay 90, permitting its armature 9| to be pulled back by the spring 92 to contact with the contact 93 to close the circuit including the valve control motor 35, the current source causing the motor 35 to close the valve 35 to shut of! the supply of moisture within the room when the wet bulb temperatures are on the wet bulb temperature curve of Fig. 7.' When the wet bulb temperatures are higher than those on the wet bulb temperature curve of Fig. 7, it is desirable that the humidifier be shut.

ofl. sothat the resulting increased electro-motive forces to be set up by the differential coil 36 which cause the moving coil 3| to rotate to the left (facing the drawings) to move the pointer 32 away from .the contact 33, causing the control motor 35 to keep the valve 36 closed. When the wet bulb temperatures are. below the values on the wet bulb temperature curve 01' Fig. '7, the magnetic forces set up by the electro-motive 'forces through the coil 24 are greater than those set up by the coil 36 and the moving coil 3| rotates to the right and moves the pointer 32 against the contact 33, closing the electrical circuit of the relay 96, causing the relay 96 to be energized by the battery 94 to pull up its armature 9| to open the circuit of the control motor 35, causing the valve 36 to be opened, thus permitting the moisture to be supplied to the humidifier 22, if, of

course, the dry bulb temperatures within the room are such thatthe valve 20 is .opened. The spring 31 has one end connected to the pointer 32 and the other end attached to the tensioning described above acts to shut oil the humidifier when the wet bulb temperatures am on the wet bulb temperature curve of Fig. '7 or below the curve for a given outside temperature. The following are the conditions which it is expected the apparatus will .meet in actual service, with an accompanying explanation-of the response of the apparatus to control the humidifier:

1. The outside temperature increases while the wet bulb inside temperature remains constant. The current through the difi'erential coil 24 is stronger 'than that through the differential coil 36 so that the galvanometer coil 3| is rotated to the right against the contact 33, closing the electrical circuit of the valve control motor 35, causing it to open the valve 36.

2. The outside temperature increases while the wet bulb temperature increases to follow the curve of Fig. 7. The currents in the two differential coils .are equal so that the galvanometer moving coil 3| remains in its mid-position away from the contact 33, leaving the circuit 01' the motor control valve open and the valve closed. If the outside temperature increases to throw the wet bulb temperature above or below the curve of Fig. 7,.when the wet bulb temperature is above the curve, the force in the coil 36 is greater than the force in the coil 24 causing the armature 3| to move the pointer 32 against the contact 33, closing the circuit of the valve control motor shutting oii the humidifier. If the wet bulb temperature is below the curve, the force exerted by the difierential coil 24 is greater than that exerted by the coil 30, the pointer v32 is rotated away from the contact 33, and the valve control motor opens the valve 36.

3. The outside temperature increases while the wet bulb temperature decreases. The current through the coil 24 is stronger than that through the coil 36. The pointer 32 is rotated against the contact 33 to cause the valve 36 to be opened by the valve control motor 35.

4. The outside temperature decreases while the wet bulb temperature remains constant. The 5 current through the coil 3|! is greater than that through the coil 24, and the pointer 32 is rotated away from the contact 33, leaving the valve control circuit open, so that the valve control motor 35 closes the valve 36.

5. The outside temperature decreases while the wet bulb temperature increases. The current through the coil 3|) is greater than that through the coil 24. The pointer 32 is rotated away from the contact 33, leaving the valve control circuit open so that the valve-control motor 35 closes the valve 36.

6. The outside temperature decreases while the wet bulb temperature decreases to remain on the wet bulb temperature curve of Fig. 'I. The currents in the two differential coils 24 and 30 are the same, the pointer 32 remains in its mid-position with the valve control circuit open, and the valve 36 closed. If the outside temperature decreases faster than the wet bulb temperature de- 25 creases, the current through the coil will be greater than that through the coil 24, causing the pointer 32 to be rotated away from the contact 33 with the valve 36 closed. Ii the wet bulb temperature decreases faster than the outside tem- 30 perature decreases, the current through the coil 24 will be greater than that through the coil 30, the pointer 32 will be rotated against the contact 33, the circuit of thevalve control motor closes and the valve 36 is opened.

7. Theoutside temperature remains constant while the wet bulb temperature increases. The current through the coil 30 is greater than that 1 through the coil 24, the pointer 32 is rotated away from the contact 33, and the valve 36 is closed.

8. The outside temperature remains constant while the wet bulb temperature decreases. The current through the coil 24 is greater than that through the coil 30, the pointer 32 is rotated against the contact 33, the circuit of the valve control motor is closed, and the valve control motor opens the valve 36.

The dry bulb control apparatus and the wet bulb control apparatus are both seen to be actuated independently to shut oil the supply of water to the humidifier when the relative humidity within the room and the temperature of the window pane approach predetermined levels which have been arrived at through experience. The humidifier is shut off when either the valve 26 or the valve 36 is closed and is turned on only when both valves are opened. With these control circuits, the relative humidity of the room is maintained at as high a level as is possible, as the temperature of the window pane falls, without condensation of the moisture occuring on the window pane.

The apparatus shown by Fig. 2 is substantially the same as that shown by Fig. 1 except that a single valve control motor 46 is used to shuTofl a single valve 46 between the humidifier 42 and its water supply 2|. Like numerals are used for like apparatus in the two figures. Instead of the contacts 62 and 83 of the dry bulb temperature galvanometer controlling one valve control motor, and the contact 33 and pointer, 32 controlling a separate valve control motor, the two sets of contacts are arranged in series in. a circuit including the single battery 41 and the will remain in operation under all other conditions.

In another embodiment of the invention, advantage is taken of the fact that moisture precipitates on the window pane when the inside temperature of the window pane is the dew point of the air within the room. The condensation occurs, therefore, only when the dry bulb and wet bulb temperaturesoi'thatportionof theairimmediately adjacent and in contact with the window pane are equal. Referring now to Figs. 3, 4, 5, and 6, the control apparatus for shutting off the humidifier, when the wet bulb and dry bulb temperatures of the air at the window pane are equal, will be explained. Figs. 3 and 4 are diagrammatic views showing the layout of the control apparatus, and Figs. 5 and 6'show structures which may be used with the diagrammatic circuits of Figs. 3 and 4.

Referring now to Figs. 3 and 4, the wet bulb thermocouple 55 is so placed adjacent'the inside surface of the window pane 5| that the current of air passing the thermocouple is cooled by the window pane to a wet bulb temperature proportional to the temperature of the window pane.

Provision is made for passing a current of air against the wet bulb thermocouple 55 to cause it to respond to wet bulb temperatures. This arrangement is shown by Figs. 5 and 6 and will be explained later. The dry bulb thermocouple 5! is arranged to be responsive to the temperatures of the window pane or. to outside temperatures which, of course, are proportional to the temperatures of the window pane. It may be mounted in the window pane or mountedoutside the window pane and immediately "adjacent thereto; The electro-motive forces generated by the wet bulb thermocouple 55 are led'through the variable resistance 55 into the diflerential cell 54 of the galvanometer 55. The electroemotive forces generated by the dry bulb thermocouple 52 are fed through the variable resistance 55 into the differential coil 51 of the galvanome fer. The moving coil 55 carries the indicator 55 which, when the currents through the two coils 54 and 51 are equal, remains in. its zero position as shown by the drawings. This is the condition when the wet bulb temperatures.

and the dry bulb temperatures are substantially the same and when the moisture in that portion of air immediately adjacent the window pane is' at the point of becoming precipitated.

Nonnally, ofcourse, the dry bulb temperature will be higher than the wet bulb temperature and the elec ive forces generated by the thermocouple I will be greater than those generated by the thermocouple 55. The magnetic forces exerted by the dlilerential coil 51 on the moving coil 55 will be greater than those by the diil'erential coil 54, causing the pointer 55 to rest against the contact 55 which closes the electrical circuit through the battery; 5|and. relay 55 to open the circuit of the control motor 55 which holds the valve 55 open, permitting moisture to be supplied from the water supply 54 to the humidifier 55. When the wet bulb and dry bulb temperatures approach each other to become the same, the magnetic forces set up by the coil 54 balance out those set up by the coil 51. The moving 'coil 55 returns the pointer 55 to its zero position, opening the relay circuit and energizing the control motor 52 to close the valve 55, thus shutting of the supply of water to the humidifier.

It is realized that it might prove difllcult to cool the wet bulb thermocouple 55 to a sufllciently low temperature to respond exactly to the wet bulb temperature of the air at the surface of the window pane, but it is a fact that the wet bulb thermocouple 55 would become cooled proportional to the temperatures of the window pane so that provision is made for adjusting the ditlerences between the current supplied by the two thermocouples when the dew point is reached. The variable resistance 55 may be decreased and the variable resistance 55 may be increased to cause the current supplied by the wet bulb thermocouple 55 to its diilerential coil 54 to equal those supplied by the dry bulb thermocouple 52 to its differential coil 51 when the dew point is reached, thus compensating for the probable tendency of the wet bulb thermocouple 55 to be cooled to a temperature slightly above the temperature of the window pane, when the dew point is reached. The two" adjustable biasing springs 55 and 51 which are arranged on each side of the pointer 55 may be tensioned to bias the pointer 55 tonne side or the other to compensate for inaccuracies of the electrical circuits, in the thermocouples, or in the galvanometer. a

Fig. 4 is a diagrammatic view of another arrangement for shutting oh the humidifier when the wetvbulb' and dry bulb temperatures of the air immediately adjacent the surface of the window pane are equal. With this arrangement, a differential galvanometer is not used. The dry bulb thermocouple 52 has shunted across its output terminals the high resistance 55. The wet bulb thermocouple 55 has shunted across its output terminals the high resistance 51. The positive sides of the two thermocouples are connected together and their negative sides are connected to the terminals of the'relay 55. With this arrangement, the electro-motive forces produced by the two thermocouples oppose each other so that when the generated electro-motive forces are equal, there will be no current flowing through the relay 55, permitting its armature 55 to be ,pulled back by the spring 15 to rest against the contact 1i to close an electrical circuit through thesolenoid 12 and the alternating current source 15, to close the valve 53, shutting oil the supply of water from the tank 54 to the humidifier 55. When the dry bulb temperature is greater than the wet bulb temperature, there will be current flow through the relay 55, cansing the armature 55 to pull upand break the drcult including the contact 1|, solenoid 12, and alternating current source 15, causing the solehold to open the valve 53, thus permitting the 55 and 51 may be adjusted to compensate for inequalities in the electro-motive forces produced by the thermocouples when the' dew point is reached, and the adjustable spring 15 may be variably tensioned by-the tensioning device" to cause the armature 55 of the relay 55 to respond to the desired value of current flowing through the relay.

Figs. 5 and 6 fllustrate a desirable arrangement for maintaining and enclosing the wet bulb and dry bulb thermocouples described in connection with Figs. 3 and 4. Since it is desirable that the control apparatus, according to more quickly to outside changes of temperature than a window pane would. The metal surface 14 of Figs. 5 and 6 may be mounted in a portion of the window, and provided on its side contacting withthe outside air, with the radiating fins 15 and on the side in contact with the air within the room, with the radiating fins I! which are arranged as shown by Fig. 6 to form an extended path through which asample of the moistened air within the room may be passed, to contact with a considerable portion of the cooled surface, so as to take on a wet bulb temperature proportional to the temperature of the surface 14. The outside fins 15, by providing maximum surface, cause the portion of the surface 14 extending into the room, to take on more quickly and more accurately the outside temperature. The fins 18 extending into the room, give considerable surface against which the sample of air to actuate the wet bulb thermocouple may contact, to lower to a greater extent, its temperature. The inside fins 16 are enclosed by the insulating material 11 which acts both to prevent the warmer temperature of the air within the room from cooling the air passing between the fins I6, and also to ranged, as shown, to provide an elongated path for a sample of air to actuate the wet bulb thermocouple 50 which is mounted adjacent the exhaust portion 18 of the passageway. The propeller fan I! is arranged over the exit 18 to draw a sample of air into the entrance of the passage, which sample of air takes the path indicated by the arrows and passes over the wet bulb thermocouple 50 and exits from the fan 19, as shown. While the passageway of the sample of air actuating the thermocouple has been elongated to cause the air to pass across the metal surface 14 three times, obviously, the circulation channels may be greaterin number or less in number, their number depending upon the circumstances surrounding a particular installation. It is believed that while a sample of air passing through the channels defined by the cooling fins 11, would not take on as low a temperature as the temperature of the air immediately adjacent the metal surface which would become condensed when its dew point is reached, the sample of air passing through the channels would unquestionably become cooled proportional to the temperature of the metal surface 14 which, in turn, is proportional to the outside temperature and to the temperature of the window pane and by adjustment of the resistanoes 53 and 56, as explained in connection with Fig. 3, the wet bulb and dry bulb thermocouples may be adjusted to give the desired electromotive forces when the air in contact with the cooled surface starts to precipitate moisture. Another advantage of using the finned metal surface 14 to co-operate with the control apparatus is that this metal surface may be cooled to a lower temperature by the outside air, this due to the increased conduction rate of the metal and to the provision of the fins. The control apparatus, by using the metal surface. can, there fore, be made to shut ofl thehumidifier at a temperature above that at which moisture would condense on the window pane, since the metal surface is cooled to a lower temperature.

The dry bulb thermocouple 52 may be mounted outsidethe window, may be mounted in contact with the window pane 5|, or may be mounted within an opening in the window pane 5| to become responsive to the temperature of the window pane. Either of these methods would be satisfactorysince the temperature of the window pane is proportional to the temperature of the outside air and adjustment may be made of the resistance 56, associated with the thermocouple 52, to compensate for the diflerence in temperature of the inside of the window pane and the temperature of the location of the thermocouple. It is only necessary that the thermocouple 52 generate electromotive forces proportional to the inside temperature of the window pane and this it would do in any of the locations mentioned above. A satisfactory location for the thermocouple '52 is shown by Fig. 5 where the metal surface 14 is drilled to receive the opening 8! in which the thermocouple 52 may be inserted. The thermocouple in this location would respond for all practical purposes to the temperature of the portion of the metal surface ll against which the sample of air containing moisture contacts to actuate the web bulb thermocouple 50.

The fan 19, shown by Fig. 6, may be actuated by a small electric motor. The metal surface, the insulating material 14, and the fan 19 may be made up as a small compact unit which may be quickly and easily associated with an ordinary window of a room, the air of which is to be humidified. The thermocouples may be enclosed within the unit. Since the unit requires in addition to the thermocouples, only a small fan, a galvanometer, and a motor operated valve for control of a humidifier, it is seen that it may be made up very cheaply. It may be housed in a decorative container occupying but little space; it is believed to require'little or no attention, and to positively control the humidifier to prevent the condensation of moisture appearing on the window pane of the window with which it is associated.

While single thermocouples have been illustrated for actuating control apparatus, it is believed to be obvious that two or more thermocouples may be connected in series, in parallel, or in series-parallel to give sufficient power to actuate thecontrol apparatus in the various embodiments of this invention.

Whereas the thermocouples Ill, 23, and 52 in Figs. 1, 2, and 3 have been illustrated and described as being placed in the outdoor air and being exposed to outdoor temperatures, it should be understood that these thermocouples could be mounted in the window panes or in the metal observation surfaces when such surfaces are used. Obviously, observation of outdoor temperatures is unnecessary except as such temperatures cool the window pane or observation surface, since the moisture condenses only when the observation surface has been cooled to the dew point of the humidified air, and this cooling is done by the outside air, which is at a lower temperature than that within the room. Therefore, in this specification and claims, when reference is made to outdoor temperatures weare referring to the temperature of the observation surface which may be a window pane or which may be a metal surface, such as shown by Figs. 5 and 6.

It is also believed to be obvious that mechanical or electrical equivalents may be substituted for the electrical or mechanical devices utilized in the embodiments of this invention which have been described. For example, thermostats are mechanlcal equivalents for electrical thermocouples, and may be substituted for the thermocouples illustrated as actuating control apparatus according to this invention. Likewise, resistances which vary with temperature, such as those used in barometers and other similar devices, may be used with potential sources in substitution for the thermocouples illustrated in this disclosure.

Whereas one or. more embodiments of the invention have been described for the purpose of illustration, it should be understood that the invention is not limited to the exact processes described as many departures may be made by those skilled in the art without departing from the spirit of the invention.

What is claimed is: i. Humidity 'control apparatus comprising means for supplying moisture to air within a room, an observation surface having a portion within the room and another portion exposed to outdoor temperatures, means responsive to the temperature of said observation surface, and means responsive to the wet bulb temperature of air immediately adjacent said observation surface, said means cooperating to decrease the amount of moisture supplied to the air within said room when said wet bulb temperature closely approaches the temperature of said observation surface.

2. Humidity control apparatus comprising means for supplying moisture to the air of a heated room, an observation surface within said room having a portion exposed to outdoor temperature, means responsive to the dry bulb temperature of the air within said room and to thetemperature of said observation surface, for decreasing the supply of moisture to the room, when for a given temperature of said observation surface, the dry bulb temperature falls below a predetermined level.

3. Humidity control apparatus comprising means for supplying moisture to the air of a heated room, an observation surfacewithin said room having a portion exposed to outdoor temperatures, and means responsive to the wet bulb temperature of the air within said room and to the temperature of said observation surface, for decreasing the supply of moisture to the room, when for a given temperature of said observation surface, the wet bulb temperature increases above a predetermined level.

4. Humidity control apparatus comprising means for supplying moisture to the air of a heated room, an observation surface within said room having a portion exposed to outdoor temperatures, means responsive to the dry bulb temperature of the air within said room and to the temperature of said observation surface for decreasing the supply of moisture to the room, when for a given temperature of said observation surface, the dry bulb temperature falls below a predetermined level, and means responsive to the wet bulb temperature of the air within said room and to the temperature of said observation surface, for decreasing the supply of moisture to the room, when for a given temperature of said observation surface, the wet bulb temperature of the air within the room rises above a predetermined level.

5. The method of preventing condensation from moistened air within a heated room on a surface having a portion exposed to outdoor temperatures, which comprises, passing a sample of moistened air within the room closely in contact with said surface to cool said sample to a wet bulb temperature approaching the temperature of said surface, analyzing the wet bulb temperature of the sample of air and the temperature of the surface, and decreasing the supply of moisture to the air when the wet bulb temperature of the sample of air closely approaches the temperature of said observation surface.

6. Humidity control apparatus comprising means for supplying moisture to the heated air within a room, an observation surface within said room having a portion exposed to outdoor temperatures, means for cooling a sample of the humidified air from the room to a temperature approaching the temperature of said surface, and means for decreasing the supply of moisture to the air within the room when the wet bulb temperature of said sample of air closely approaches the temperature of said surface. I

'1. Humidity control apparatus comprising a humidifier for supplying moisture to the air of a heated room, an observation surface within said room having a portion exposed to outdoor temperatures, means responsive to the dry bulb temperature of the air within said room for translating changes in temperature into movement in apparatus, means responsive to the temperature of said observation surface for translating changes in temperature into movement of apparatus, and means actuated by said apparatus acting to de crease the amount of moisture supplied by said humidifier when for a given temperature of said observation surface the dry bulb temperature of the air falls below a predetermined level.

8. Humidity control apparatus comprising a humidifier for supplying moisture to the air of a heated room, an observation surface within said room having a portion exposed to outdoor temperatures, means responsive to the wet bulb temperature of the air within said room for translating changes'in temperature into movement in apparatus, means responsive to the temperature of said observation surface for translating changes in temperature into movement of apparatus, and means actuated by said apparatus acting to increase the amount of moisture supplied by said humidifier when for a given temperature of said observation surface the wet bulb temperature of the air increases abovea predetermined level.

9. Humidity control apparatus comprising a humidifier for supplying moisture to the air of a heated room, an observation surface within said room having a portion exposed to outdoor temperatures, means responsive to the dry bulb temperature of the air within said room and to the temperature of said observation surface for translating temperature changes into movement of apparatus, which, when for a given temperature of said observation surface the dry bulb temperature of the air falls below a predetermined level, acts to decrease the supply of moisture to the room, and means responsive to the wet bulb temperature of the air within the room and to the temperature of said observation surface acting to translate temperature changes into movement of apparatus which, when for a given temperature of said observation surface the wet bulb temperature of the air within the room rises above a predetermined level, acts to decrease the supply 0 moisture from said humidifier.

10. Humidity control apparatus comprising a humidifier for supplying moisture to the air of a heated room, an observation surface within said room having a portion exposed to outdoor temperatures, means responsive to the dry bulb temperature of the air within said room and to the temperature of said observation surface for translating temperature changes into movement of apparatus, which, when for a given temperature of said observation surface the dry bulb temperature of the air increases above a predetermined level, acts to increase the supply of moisture to the room, and means responsive to the wet bulb temperature of the air within the room and to the temperature of said observation surface acting to translate temperature changes to movement of apparatus which, when for a given temperature of said observation surface the wet bulb temperature of the air within the room falls below a predetermined level, acts to increase the supply of moisture from said humidifier.

' ll. Humidity. control apparatus comprising a humidifier for supplying moisture to the air of a heated room, an observation surface within said room having a portion exposed to outdoor temperatures, an insulating enclosure adjacent a portion of said observation surface, means for passing a sample of the humidified air from the room through said enclosure to cool the sample to a temperature approaching the temperature of said surface, means responsive to the wet-bulb temperature of said sample of air, means responsive to the temperature of that portion of said surface which contacts with the sample of said air, and control apparatus actuated by the two last mentioned means for decreasing the supply of moisture to the air within a room when said temperatures closely approach each other.

12. Humidity COI1tI'O1 apparatus for theconditioning of air in cold weather, comprising means for supplying moisture to the air of a heated room,

" an observation surface within said room and having a portion exposed to outdoor temperatures, means responsive to air conditions within the enclosure for adjusting said first mentioned means for controlling the supply of moisture to the air within said room, and means responsive to outdoor temperatures for adjusting said last mentioned means to control the operation thereof for automatically decreasing the supply of moisture conformably with the lowering of outdoor temperatures so as to prevent the condensation of moisture in the heated air, on said surface.

13. Humidity control apparatus for use in winter, comprising means for supplying moisture to heated air within a room, an observation surface within said room and having a portion exposed to outdoor temperatures, control means for varying the effect of said means upon the heated air, and means responsive to changes in wet and dry bulb temperatures indoors and to outdoor temperatures for adjusting said control means for automatically lowering the relative humidity of the heated air conformably withthe lowering of the outdoor temperature so as to prevent the condensation of moisture in the heated air, on said surface.

14. Humidity control apparatus for use in winter, comprising means for supplying moisture to heated air within a room, an observation surface within said room and having a portion exposed to outdoor temperatures, control means for varying the effect of saidmeans upon the heated air, and means responsive to changes in relative humidity indoors and to outdoor temperatures for adjusting said control means for automatically lowering the relative humidity of the heated air conformably with the lowering of the outdoor temperature so as to prevent the condensation of moisture in the heated air, on said surface.

15. Humidity control apparatus for use in winter, comprising means for supplying moisture to heated air within a room, an observation surface within said room and having a portion exposed to outdoor temperatures, control means for varying the effect of said humidifier upon the heated air. and means responsive to changes in relative humidity indoors and to outdoor temperatures for adjusting said control means for automatically lowering the relative humidity of the heated air when a fall in outdoor temperature chills said surface to a temperature which closely approaches the dew point of the indoor air so as to prevent the condensation of moisture in the heated air, on said surface.

16. Humidity control apparatus for use in winter, comprising means for supplying moisture to the air of a heated room, an observation surface within said room and having a portion exposed to outdoor temperature, control means for varying the effect of said means upon the heated air, and means responsive to humidity changes within the room and to outdoor temperatures for adjusting said control means for automatically decreasing the supply of moisture when the outdoor temperature falls below a predetermined level fora predetermined indoor relative humidity so as to prevent the condensation of moisture in the heated air, on said surface, and for automatically increasing the supply of moisture to the heated air when the outdoor temperature rises above a predetermined level for a. pre-, determined indoor relative humidity.

17. Humidity control apparatus for use in winter, comprising means for supplying moisture to the heated air of a room, an observation surface within said room and having a portion exposed to outdoor temperatures, control means for varying the effect of said means upon the heated air, and means responsive to air conditions within said room, and to outdoor temperatures for adjusting said control means for automatically decreasing the supply of moisture to the heated air when the outdoor temperature falls below a predetermined level for a predetermined indoor relative humidity so as to prevent the condensation of moisture in the heated air, on said surface, and for automatically increasing the supply of moisture to the heated air when the outdoor temperature rises above a predetermined level for a predetermined indoor relative humidity.

18. Humidity control apparatus for use i winter, comprising means for supplying moisture to the heated air within a room, an observation surface within said room and having a portion exposed to outdoor temperatures, control means for varying the effect of said means upon the heated air, and means responsive to humidity indoors and to outdoor temperatures for adjusting said. control means for automatically lowering the relative humidity of the heated air when the outdoor temperature falls below a predetermined level for a predetermined indoor relative humidity so as to prevent the condensation of moisture in the heated air, on said surface and for automatically increasing the relative humidity of the heated air when the outdoor temperature rises above a predetermined level for a predetermined indoor relative humidity. l 19. Humidity control apparatus 'tor use i winter, comprising means for supplying moisture to heated air within a room, an observation surface within said room and having a portion exposed to outdoor temperatures, control means for varying the effect 0! said means upon the heated air, and means responsive to changes in relative humidity indoors and to outdoor temperatures for adjusting said control means for automatically decreasing the supply of moisture to the heated air when the outdoor temperature falls below a predetermined level for a predetermined indoor relative humidity so as to prevent the condensation oi moisture in the heated air, on said surface and for automatically increasing the supply of moisture to the heated air when the outdoor temperature rises above a predetermined level for a predetermined indoor relative humidity.

20. Humidity control apparatus for use in winter, comprising means for increasing the moisture content oi heated air within a room, an observation surface within said room and having a portion exposed to outdoor temperatures, control means for varying the eiiect 01 said means upon the heated air, and means responsive to humidity changes in the heated air and to outdoor temperature ior adjusting said control means for automatically decreasing the supply of moisture to the heated air when the outdoor temperature falls below a predetermined level for a predetermined indoor wet and dry bulb temperature so as to prevent the condensation 0! moisture in the heated air, on said surface and for automatically increasing the supply of moisture to the heated air when the outdoor temperature rises above a predetermined level tor a predetermined indoor wet and dry bulb temperature.

21. Humidity control apparatus ior use in winter, comprising means for increasing the moisture content of heated air within a room, an observation surface within said room and having a portion exposed to outdoor temperatures, control means for varying the effect oi said means upon the heated air, and means responsive to changes in wet and dry bulb temperatures in the heated air and to outdoor temperature ior adjusting said control means for automatically decreasing the supply of moisture to the heated air when the outdoor temperature falls below a predetermined level for a predetermined indoor wet and dry bulb temperature so as to prevent the condensation of moisture in the heated air, on said surface and for automatically increasing the supply of moisture to the heated air when the outdoor temperature rises above a predetermined level for a predetermined indoor wet and dry bulb temperature.

22. Humidity control apparatus comprising means for supplying moisture to the heated air within a room, a window pane within said room exposed on one side to outdoor temperatures, means located in said room at a point in close proximity to said window pane for determining the condition of the air immediately adjacent said window pane, and means actuating said first mentioned means for decreasing the supply of moisture to the air within the room .when said window pane is chilled by a change in outdoor temperature to a temperature approaching the dew point temperature of the air at said point and the air at said point approaches 100% relative humidity.

SAMUEL M. ANDERSON.

ROBERT T. PALMER. 

